Interpretive Summary: Developing integrated pesticide management (IPM) programs for plum curculio, Conotrachelus nenuphar (Herbst), in highbush blueberries, Vaccinium corymbosum L, is challenging due to changing regulations. We conducted field, semi-field, and laboratory experiments to determine the efficacy of different classes of insecticides against eggs, larvae, and adult plum curculios. We found that the phosmet and indoxacarb were effective against adults but novaluron was not. Novaluron did reduce larval emergence from fruit when applied prior to bloom. In semi-field experiments, it also resulted in a decrease in numbers of oviposition scars and eggs on fruit. In laboratory studies, phosmet, acetamiprid, and thiamethoxam were effective against larvae already present in the fruit, whereas fenpropathrin, indoxacarb, and novaluron were less so. Residue profiles showed depth of penetration of different insecticides. We believe a pre-bloom novaluron application in combination with a post-bloom insecticide treatment aimed at adults and larvae is a good approach to manage multiple lifestages of this important pest.

Technical Abstract:
Ongoing regulatory changes are eliminating or restricting the use of broad-spectrum insecticides in fruit crops in the USA, and current IPM programs for plum curculio, Conotrachelus nenuphar (Herbst), in highbush blueberries, Vaccinium corymbosum L, need to address these changes. To assist in this process, field, semi-field, and laboratory experiments were conducted to determine the efficacy of different classes of insecticides against various stages of C. nenuphar in blueberries. In the field, post-bloom applications of the organophosphate phosmet and the oxadiazine indoxacarb showed significant adulticidal activity. In contrast, the insect growth regulator novaluron had no effect on adults but reduced larval emergence by greater than 60 percent when applied pre-bloom. In semi-field experiments, novaluron applications resulted in a decrease in numbers of oviposition scars and eggs on fruit. In laboratory bioassays, phosmet and the neonicotinoids acetamiprid and thiamethoxam showed significant curative activity on C. nenuphar larvae when applied topically to infested fruit. In comparison, the pyrethroid fenpropathrin, indoxacarb, and novaluron were weaker curative agents. Residue profiles showed that phosmet and acetamiprid residues are almost equally distributed between the skin and the interior blueberry flesh, indicating that substantial portions of residues penetrated the fruit; whereas fenpropathrin and novaluron had the lowest levels of penetration. In blueberries, novaluron showed anti-ovipositional/ovicidal activity; phosmet and indoxacarb showed adulticidal activity; while phosmet and the neonicotinoids showed best curative (larvicidal) control on C. nenuphar. We discuss the utility of a novel pre-bloom novaluron application in combination with a post-bloom treatment of an adulticidal/larvicidal insecticide for optimal multi-stage control of C. nenuphar in blueberries.